Along about July 1944, as Group Bombing Officer I was at Head-quarters preparing data for a mission. I seem to remember that I was a Captain at the time. On this occasion we were honored by the presence of what I assumed to be an inspection team from either Wing or Bomber Command. On my desk I had a Field Order containing a new weather report for the target area. As I recall this report said the wind would be out of the West at 23 knots. This inspection team Lt. Col. was standing behind me as I worked. He tapped me on the shoulder and told me he thought I had just made a mistake in my calculations. He pointed out that I should be using 23 knots as shown in the Field Order. I told him that I was using 19 knots because that is about what I thought it would be over the target by the time we arrived there. He got a little upset that I would question the forecast of some of the top meteorologists in the entire world. I didn't argue. I just stood up and pulled out my wallet. I asked him how much he would like to bet that 19 wouldn't be nearer to correct than 23, to be determined by the lead crew after the mission was over. He just turned and walked away.
The lead crew usually takes a double-drift reading on a mission to get a final check on the wind direction and velocity for both navigation and bombing purposes. Occasionally, there is no opportunity. But, all that is needed is to fly straight and level on two different headings for a couple of minutes each with good visibility of the ground below. The bombsight is the perfect double-drift instrument. So, when the lead crew reports the result of their mission I felt sure they could settle our bet. My visitor did not bet with me but you can be sure he checked it out. I know I did. In this instance I would have won.
For some time I had known that our forecasts were good on wind direction but too high on velocity. The readings given were taken in the middle of the night. The variation seemed to be caused by the sun heating up the earth somewhat by the time we arrived over the target. This heat would cause the air to rise vertically, which slows down the horizontal velocity. This is strictly a land characteristic. It would not be true over water.
I tried to get Bomber Command to apply this thermal factor to their forecast. They refused, saying that they were required to give out the latest, most accurate readings in the target area. I said, "O.K.". From then on I continued to apply my own factor to each Field Order.
Albert E. Hill